In the process of preparing a warp loom beam for weaving, warp yarns are delivered through a slasher apparatus which includes a size box which applies a protective coating of size to the yarns. The size holds the yarns together during weaving and prevents the threads from being chafed.
Water is typically used as the dissolving medium in which the size is dissolved and disbursed to aid in uniform application to the warp yarns. A ten percent add-on weight of size is a commonly acceptable amount, and a ten percent solution of solids (size) and ninety percent water is normally utilized. This requires that a considerable amount of water be squeezed and dried out of the yarns for every pound of size that is applied to the yarns.
Conventional size boxes include an immersion roll which is immersed in a sizing material in the size box. The warp yarns pass under the immersion roll and then between a pair of pressure rolls where some of the excess size is squeezed out. However, considerable water remains to be removed and dried out of the yarns after application of the size.
In an attempt to eliminate the application of excessive water to the yarns which thereafter must be removed by drying, requiring considerable amounts of energy, a method is proposed in U.S. Pat. No. 4,364,157 of applying only a very small, metered amount of concentrated size solution to the yarns. In this method, the yarns do not become immersed in the size material, but rather pass between an application roll and a pressure roll. A metered amount of sized is applied to the outside of the application roll which is pressed into the yarns at the nip of the rolls. The application roll is partially immersed in the size material in the size box, but the excess size is removed by a doctoring or other means before the size is applied to the warp yarns. In this method, a metered amount of sizing material is applied without a sacrifice in the strength of the warp yarns.
While various porous, engraved, etched, and grooved rolls have been utilized heretofore, as simple application rolls for applying fluid to yarns and strands, these have generally not been utilized in size boxes or the metering of size, apparently due to the inherent problems occurring in the adhesive and chemical nature of the size. Examples of such rolls are shown in U.S. Pat. Nos. 3,306,254; 3,157,536; 3,553,006; 4,268,550; and British Pat. No. 23,955, many of which are related to single strand fluid treatment.
In British Pat. No. 742,308, a device for dry sizing of threads is disclosed which includes a rotating sieve roll to which a batch of threads are brought into contact. A dry size, containing no water, is applied through a perforated jacket and an outer brush-like covering. The method and apparatus thus differ from the conventional application of a wet size with water utilizing an application and pressure roll. The control of the amount and nature of the size coating applied by the British device would not be satisfactory and exact for use in modern slashing processes.
While the metering of the sizing material on the outside of the roll as disclosed in U.S. Pat. No. 4,364,157 is an entirely suitable process, the precision machining of the doctoring blade and roll surface involve a good deal of expense and skill in order to provide the required precise metering effect. Varying the amount of the metered size during the sizing process such as for different warp styles becomes difficult, often requiring change out of the application roll in the case of a patterned roll.
Accordingly an important object of the present invention is to provide an apparatus and method for applying size to warp yarns wherein a metered amount of size is applied to the warp yarns.
Still another important object of the present invention is to provide an apparatus and method for applying size to warp yarns in a metered amount wherein the size material is applied from the inside of an application roll outwards to an exterior application surface of the roll, thus simplifying many problems of applying size material in metered amounts.
Still another important object of the present invention is to provide an apparatus and method for varying, in a controlled manner and over a given range continuously during the sizing process, the amount of the metered size to be applied to warp yarns such that different warp styles requiring different size add-on values can be prepared with the same applicator roll.
Still another important object of the present invention is to provide an apparatus and method for applying a size material in a highly precise metered amount with a porous metering and application roll which is maintained moist regardless of the delivery of size therethrough.
Still another important object of the present invention is to provide a method and apparatus for applying a metered amount of size to warp yarns during a slashing process wherein an application roll having layers of different porosity is utilized to control the metering and distribution of the size material onto the yarns.